Preforms for use in manufacturing composite structures and methods of making such preforms

ABSTRACT

A preform manufactured by an additive manufacturing process is provided. The preform may include an annular fibrous layer made from a polymeric material, such as PAN. The annular fibrous layer may comprise one or more of a non-uniform areal weight profile, non-uniform fiber volume profile, and a non-uniform fiber density profile. Such profiles may vary in either or both of the radial and axial directions, as well as in localized regions of the preform.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to, U.S.application Ser. No. 14/312,155, filed Jun. 23, 2014 and titled“PREFORMS FOR USE IN MANUFACTURING COMPOSITE STRUCTURES AND METHODS OFMAKING SUCH PREFORMS,” which is hereby incorporated by reference in itsentirety.

FIELD

The present disclosure relates to components of wheel and brakeassemblies, and more specifically, to preforms made using additivemanufacturing.

BACKGROUND

Conventional carbon composite formation includes creating a net-shapedpreform using a circular needle loom (CNL). However, CNLs typicallyproduce orthogonal (rectangular) structures that are then punched or cutinto circular/annular systems/structures creates waste scrap products.Further, fabric-based preforms are limited in their design by thecharacteristics of the fabrics, as well as the multiple layers of fabricrequired to produce the preform.

SUMMARY

An exemplary preform may comprise an annular fibrous layer having afirst surface, an inner diameter, an outer diameter, a radius, an axisand a commercially viable thickness, wherein the annular fibrous layercomprises a predetermined areal weight profile, a predetermined fibervolume profile, and a predetermined fiber density profile, at least oneof which is non-uniform. The annular fibrous layer may be formed by anadditive manufacturing process. The preform may include a lug section,wherein a fiber density profile along one of a radius or an axiscomprises a fiber density that is greater at a point at or near the lugsection than a fiber density at the inner diameter. A predeterminedareal weight profile, predetermined fiber volume profile, and/or apredetermined fiber density profile may vary along the radius such thatthe areal weight, fiber volume, and/or fiber density is greater at apoint along the outer diameter than at a point along the inner diameter.The predetermined areal weight profile, predetermined fiber volumeprofile, and/or predetermined fiber density profile may vary along theaxis such that the areal weight, fiber volume, and/or fiber density isgreater at or near a first surface than at a point approximately half ofthe thickness of the annular fibrous layer.

A method for manufacturing a preform using an additive manufacturingprocess may comprise defining a preform design comprising an annularfibrous layer having an axis and a radius and one of a non-uniformpredetermined areal weight profile, a non-uniform predetermined fibervolume profile, or a non-uniform predetermined fiber density profile,and forming the preform design using an additive manufacturing process,such as a fused deposition modeling process. The preform design mayfurther comprise a lug section, wherein a fiber density profile alongone of a radius or an axis comprises a fiber density that is greater ata point at or near the lug section than a fiber density at an innerdiameter of the preform design. The annular fibrous layer may comprise anon-uniform areal weight profile, a non-uniform fiber volume profile,and/or a non-uniform fiber density profile that varies along the radiusand/or the axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

FIGS. 1A and 1B illustrate a top view and a side view, respectively, ofa preform in accordance with the present disclosure;

FIGS. 2A and 2B illustrate cross sectional views of a preform inaccordance with the present disclosure; and

FIG. 3 is a process flow diagram for making a preform with additivemanufacturing, in accordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration. While these exemplary embodiments are described insufficient detail to enable those skilled in the art to practice theinventions, it should be understood that other embodiments may berealized and that logical changes and adaptations in design andconstruction may be made in accordance with this invention and theteachings herein. Thus, the detailed description herein is presented forpurposes of illustration only and not of limitation. The scope of theinvention is defined by the appended claims. For example, the stepsrecited in any of the method or process descriptions may be executed inany order and are not necessarily limited to the order presented.Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact.

Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step.

As used herein, the term “additive manufacturing” encompasses any methodor process whereby a three-dimensional object is produced by creation ofa substrate or material, such as by addition of successive layers of amaterial to an object to produce a manufactured product having anincreased mass or bulk at the end of the additive manufacturing processthan the beginning of the process. In contrast, traditionalmanufacturing (e.g., forms of subtractive manufacturing) by machining ortooling typically relies on material removal or subtractive processes,such as cutting, lathing, drilling, grinding, and/or the like, toproduce a final manufactured object that has a decreased mass or bulkrelative to the starting workpiece. Other traditional manufacturingmethods includes forging or casting, such as investment casting, whichutilizes the steps of creating a form, making a mold of the form, andcasting or forging a material (such as metal) using the mold. As usedherein, the term “additive manufacturing” should not be construed toencompass fabrication.

A variety of additive manufacturing technologies are commerciallyavailable. Such technologies include, for example, fused depositionmodeling, polyjet 3D printing, electron beam freeform fabrication,direct metal laser sintering, electron-beam melting, selective lasermelting, selective heat sintering, selective laser sintering,stereolithography, multiphoton photopolymerization, and digital lightprocessing. These technologies may use a variety of materials assubstrates for an additive manufacturing process, including variousplastics and polymers, metals and metal alloys, ceramic materials, metalclays, organic materials, and the like. Any method of additivemanufacturing and associated compatible materials, whether presentlyavailable or yet to be developed, are intended to be included within thescope of the present disclosure.

Typical carbon composite brake pads are formed by creating a preform,then using the preform to form the carbon composite brake pad.Carbon-carbon C/C material is generally formed by utilizing eithercontinuous oxidized polyacrylonitrile (PAN) fibers, referred to as “OPF”fibers or carbonized carbon fibers, referred to herein as carbon fibers.Such fibers are used to fabricate a preform shape using a needlepunching process. OPF fibers or carbon fibers are layered in a selectedorientation into a preform of a selected geometry. Typically, two ormore layers of fibers are layered onto a support and are then needledtogether simultaneously or in a series of needling steps. This processinterconnects the horizontal fibers with a third direction (also calledthe z-direction). The fibers extending into the third direction are alsocalled z-fibers. This needling process may involve driving a multitudeof barbed needles into the fibrous layers to displace a portion of thehorizontal fibers into the z-direction.

Conventionally, a yarn or fiber tow is laid radially to form an annulardisc shaped preform layer from the inner diameter of the preform (the“ID”) to the outer diameter of the preform (the “OD”). Gaps typicallyoccur between the fiber tows farther from the ID. Stated another way,when viewed with respect to unit areal weight, e.g., the amount of massper area, extending from the inner diameter to the outer diameter, thefiber tow volume and/or the areal weight decrease due to larger gapsbetween the adjacent fiber tows. Alternatively, overlapping occurs atthe ID which leads to uneven surfaces.

For instance, during a chemical vapor infiltration/chemical vapordeposition process, carbon may be deposited onto fiber tows. However, ifno fiber tows are present, such as in the case of a gap, then the carbondeposition process is stymied. This may create a pore in thecarbon-carbon composite. Pores in a carbon-carbon composite may collectdebris, fluid, gas, etc. Further, pores may lead to oxidation.Conventional attempts to reduce these issues may include layeringsectors of a disc shape preform from a two dimensional fabric cut fromanother shape, such as a rectangular shaped piece of fabric. Thesesectors may be overlapped or abutted as predetermined. Discontinuitiesmay result from the joint locations of two abutted sectors and/or at theoverlapping layers. A layer of a preform where discontinuities areobserved likely results in a non-uniform areal weight. For instance, inthe case where two sectors overlap by half an inch, in that half an incharea the areal weight is double that of the rest of the layer. This maycreate high spots and low spots in the layer. Also, in the case ofabutted sectors, if the abutted areas are layered the composite strengthis greatly reduced.

Other properties of preforms include fiber volume and fiber density. Asused herein, “fiber volume” refers to the percentage or fraction of aspecified volume within a specific portion or segment of a preform thatis occupied by fiber. As used herein, “fiber density” refers to the massof fiber contained in a specified volume within a specific portion orsegment of a preform.

As used herein, “profile” refers to the contour and characteristics of agiven property in a specific direction or orientation within a preform.For example, a “fiber volume profile” in a radial direction would referto the specific quantitative values of the fiber volume at variouspoints along the radial direction, including the manner in which thefiber volume changes or remains uniform or constant in the radialdirection.

As used herein, “predetermined” refers to a characteristic ororientation that is designed, planned, or otherwise calculated. Forexample, a “predetermined fiber volume profile” would refer to a fibervolume profile that is intended and desired, as opposed to a fibervolume profile that was unplanned, unintended, and/or undesired.

Therefore, a preform having predetermined characteristics, such as apredetermined areal weight, fiber volume, and fiber density at variouspoints in the preform may be beneficial. As will be discussed in greaterdetail, forming a preform using additive manufacturing methods such asthree-dimensional polymeric printing may provide the ability to vary oneor more of these characteristics. Further, although a preformmanufactured using three-dimensional polymeric printing does notnecessarily comprise a plurality of fibers, for the sake of consistencyand clarity, various attributes and aspects of the present disclosurewill be described with reference to fiber characteristics (such as, forexample, fiber volume and fiber density).

Further, a preform formed as a single layer would eliminate the need toneedle multiple layers of fabric together to achieve a commerciallyviable thickness. In addition, forming a preform in its predeterminedannular shape may eliminate a significant amount of wasted fibrousfabric material.

With reference to FIGS. 1A and 1B, a preform 100 is illustrated. Invarious embodiments, preform 100 comprises an annular shape having aninner diameter 104 and an outer diameter 106. Further, preform 100 maycomprise, for example, a first surface 108. Further, preform 100 maycomprise a thickness “t.”

In various embodiments, preform 100 comprises a single annular fibrouslayer 102. As previously discussed, although annular fibrous layer 102is described as “fibrous,” it may, in fact, comprise non-fibrousstructures or portions. Annular fibrous layer 102 may comprise a singlelayer formed by a three-dimensional printing process, as will bediscussed further. For example, annular fibrous layer 102 may comprise aplurality of individual fibers, a single fiber, non-fibrous structures,or any combination thereof. In various embodiments, “t” is acommercially viable thickness of preform 100. Stated another way, singleannular fibrous layer 102 comprises a single layer of thickness “t,” anddoes not require the combination of multiple fabric-based layers toproduce a commercially viable preform 100.

For example, and with reference to FIGS. 2A and 2B, annular fibrouslayer 102 may comprise one or more fibers, such as, for example, fibers210 a and 210 b. In various embodiments, fibers 210 a and 210 b may havedifferent configurations and/or shapes from each other. Further, fibers210 a and 210 b may have different characteristics from each other,including thickness, composition, and density, among othercharacteristics. Further, various characteristics of fibers 210 a and210 b may be varied along the length of the fibers to producepredetermined properties of annular fibrous layer 102 and preform 100.For example, fibers 210 a and/or 210 b may comprise a thickness,density, composition, or cross sectional shape that varies along itslength.

Fibers 210 a and 210 b may be oriented differently relative to oneanother throughout annular fibrous layer 102. Such orientation mayproduce predetermined properties in preform 100 and, consequently, in aresulting carbon composite structure produced from preform 100. As willbe discussed further, the orientation of fibers 210 a and 210 b and/orthe characteristics of fibers 210 a and 210 b may be varied to producepredetermined properties in preform 100.

Annular fibrous layer 102 may comprise a radius 212 and an axis 214. Invarious embodiments, one or more characteristics of annular fibrouslayer 102 may vary in relation to radius 212, axis 214, or both. Thisvariation may be a result of the orientation of fibers, such as, forexample, fibers 210 a and 210 b, and/or a result of the difference incharacteristics of fibers 210 a and 210 b.

In various embodiments, annular fibrous layer 102 may comprise a radialsegment 220. Radial segment 220 may comprise, for example, variouscharacteristics such as areal weight, fiber volume, and fiber density,among others. In various embodiments, such characteristics may varyalong a radius 212 within radial segment 220 according to apredetermined profile. For example, annular fibrous layer 102 maycomprise a predetermined areal weight profile along radius 212 withinradial segment 220. The areal weight profile may comprise variousdifferent areal weights along radius 212. In various embodiments, anareal weight along radius 212 at outer diameter 106 may differ from anareal weight along radius 212 at inner diameter 104. For example, alongradius 212, an areal weight at outer diameter 106 may be greater than anareal weight at inner diameter 104. The areal weight profile may vary inany predetermined manner, including having little or no variance alongradius 212 (e.g., a “uniform” areal weight profile). For example, a“uniform” areal weight profile may comprise a constant areal weightalong the profile, including a constant areal weight along radius 212.In other embodiments, the areal weight profile may vary significantlybetween various points along radius 212.

In various embodiments, annular fibrous layer 102 may comprise an axialsegment 222. Similarly to radial segment 220, axial segment 222 maycomprise characteristics such as areal weight, fiber volume, and fiberdensity, among others. In various embodiments, such characteristics mayvary along an axis 214 within axial segment 222 according to apredetermined profile. For example, annular fibrous layer 102 maycomprise a predetermined areal weight profile along axis 214 withinaxial segment 222. In various embodiments, along axis 214, an arealweight at outer diameter 106 may differ from an areal weight along axis214 at inner diameter 104. For example, along axis 214, an areal weightat first surface 108 may be greater than an areal weight atapproximately half of thickness “t.” An areal weight profile may vary inany predetermined manner, including little or no variance along axis 214(a “uniform” areal weight profile), or significantly between variouspoints along axis 214.

For example, an areal weight profile may comprise a three dimensionalprofile which varies along both axis 214 and radius 212. In oneembodiment, the areal weight profile varies such that areal weight isgenerally higher in the vicinity of outer diameter 106 than innerdiameter 104, and generally higher in the vicinity of first surface 108than at approximately half of thickness “t” (e.g., the center of preform100). The areal weight profile may vary in any manner that providespredetermined characteristics to preform 100, which may subsequentlyprovide predetermined characteristics to a carbon composite brake padproduced from preform 100. Such predetermined characteristics of acarbon composite brake pad may include, for example, improved strength,improved wear resistance, and improved oxidation resistance, amongothers.

Similarly to a predetermined areal weight profile, annular fibrous layer102 may comprise a predetermined fiber volume profile. As previouslydescribed, the characteristics and orientation of fibers such as fibers210 a and 210 b may be varied to provide a predetermined fiber volumeprofile. In various embodiments, a predetermined fiber volume profilemay vary along radius 212 of radial segment 220 and/or axis 214 of axialsegment 222 to provide predetermined characteristics to a resultingcarbon composite brake pad formed from preform 100. In otherembodiments, the fiber volume profile may have little or no variancealong radius 212 and/or axis 214.

Further, annular fibrous layer 102 may comprise a predetermined fiberdensity profile. In various embodiments, a predetermined fiber volumeprofile may vary along radius 212 of radial segment 220 and/or axis 214of axial segment 222 to provide predetermined characteristics to aresulting carbon fiber brake pad formed from preform 100. In otherembodiments, the fiber volume density may have little or no variancealong radius 212 and/or axis 214.

In various embodiments, characteristics of annular fibrous layer 102 mayvary at localized regions. For example, at least one of an areal weight,fiber volume, and fiber density may be greater at a localized regionwhere additional strength, improved wear resistance, or improvedoxidation resistance are predetermined. In various embodiments, preform100 may comprise a lug section 116. Lug section 116 may, for example,couple a carbon composite structure formed from preform 100 to anothercomponent of a braking system. In such embodiments, one or more of anareal weight, fiber volume, and fiber density may be greater at or nearlug section 116 than at other positions of annular fibrous layer 102 toimprove the strength of the resulting carbon composite structure in andaround lug section 116. Although described in relation to a specificlocal region of preform 100, characteristics such as areal weight, fibervolume, and fiber density may be varied in any region of annular fibrouslayer 102.

In various embodiments and with reference to FIG. 3, a method for makinga preform using additive manufacturing 300 may include defining apreform design (step 330). For example, step 330 may comprise using,among other techniques, two dimensional modeling techniques to define apreform design which comprises an annular fibrous layer having at leastone of a non-uniform areal weight profile, a non-uniform fiber volumeprofile, or a non-uniform fiber density profile. In various embodiments,step 330 comprises designing a preform that may only be produced by anadditive manufacturing technique. Such a design may include fiberproperties and orientations that are not possible with conventional,fabric- or textile-based methods. Further, producing the preform in asingle fibrous layer may eliminate the requirement of needling togethermultiple layers of fabric, which in turn may save time and expense. Inaddition, printing the preform in its final annular configuration mayreduce waste associated with forming the preform in a rectangularconfiguration and reducing it to the annular configuration.

In various embodiments, the preform design of step 330 is thenmanufactured using an additive manufacturing technique (step 340). Forexample, step 340 may comprise using a three dimensional polymericprinting technique such as a fused deposition modeling process tomanufacture a preform, such as preform 100, having the sameconfiguration as the preform design of step 330.

In various embodiments, method 300 may further comprise a carbonizationof the preform step 350. For example, step 350 may comprise conventionalcarbonization techniques which convert the preform to a carbon compositestructure such as, for example, a carbon composite brake pad.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosure. The scope of the disclosure is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”,“various embodiments”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f) unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A method for making a preform comprising:defining a preform design, wherein the preform design comprises anannular fibrous layer having an axis and a radius and one of anon-uniform predetermined areal weight profile, a non-uniformpredetermined fiber volume profile, or a non-uniform predetermined fiberdensity profile; and forming the preform design using an additivemanufacturing process.
 2. The method of claim 1, wherein the additivemanufacturing process comprises a fused deposition modeling process. 3.The method of claim 1, wherein the preform design further comprises alug section, wherein the non-uniform fiber density profile along atleast one of the radius or the axis comprises a fiber density that isgreater at a point in the lug section than a fiber density at an innerdiameter of the preform design.
 4. The method of claim 1, wherein theannular fibrous layer includes the non-uniform areal weight profilewhich varies along one of the radius or the axis.
 5. The method of claim1, wherein the annular fibrous layer includes the non-uniform fibervolume profile which varies along at least one of the radius or theaxis.
 6. The method of claim 1, wherein the annular fibrous layerincludes the non-uniform fiber density profile which varies along one ofthe radius or the axis.